1. Field of the Invention
This invention relates to an intermediate amplifier for a system intended for communications transmission using light waves passing through optical wave guides, and more particularly to such an amplifier which comprises an optical amplifier for amplifying the light waves on the laser principle.
2. Description of the Prior Art
An optical intermediate amplifier is disclosed in German patent application P 21 47 842.2 in which an optical intermediate amplifier operating as a laser amplifier amplifies light signals in a doped semiconductor monocrystal which functions as the active medium. One embodiment of the optical amplifier utilizes a doped monocrystal semiconductor which is electrically pumped and which is disposed between and coupled to the ends of a pair of light conductors. If desired, the end surfaces of the semiconductor laser are inclined toward each other to reduce undesirable oscillations in the semiconductor material. Resonator mirrors are provided in another embodiment of the invention to reflect the amplified light signals several times to obtain the desired mode in the amplified light signals which are then directed back through the same conductor and subsequently separated therefrom by branching to a separate conductor. In another embodiment, the material forming the laser amplifier is provided with mirrors which are arranged to produce a zig-zag path through the amplifying material for exit in a separate conductor in a direction opposite to the direction of incidence. In still another embodiment an optical active material of a solid state laser is applied to a portion of a circumferential shell of a light conductor, and the active material is optically pumped to amplify surface waves in the shell to obtain the amplified signal for the information transmission system. Through the utilization of integrated techniques, each embodiment is preferably formed with the wave conductor.